An optical beacon is currently provided on automatic command to line-of-sight guided missiles, providing a unique missile signature for automatic tracking and guidance. This signature attempts to provide discrimination against deliberate false targets such as flares, search lights, and other optical jammers. Discrimination should also be provided against normal background interference such as glare, reflection, and fires. These optical signatures, transmitted from missiles, provide a relatively low frequency signal output and are susceptible to optical jammers (false targets) having this same frequency capability.
Typically, a coded light source (active beacon) on the missile is automatically tracked by a tracker located at a launching site. This tracker is also bore-sighted to an optical telescope through which a gunner observes the target. Thus if the gunner places the telescope crosshairs on a target, the tracker mull axis will also be along this same line-of-sight to the target. The tracker output represents an angular deviation of the coded light source from the line-of-sight and it is used to generate correctional guidance commands to return the missile to the line-of-sight. The missile, through correctional guidance, remains on this line-of-sight trajectory until impact with the target.
A variety of devices have been used as the light source which enables the tracker to identify the missile. A pyrotechnic device, the railroad flare, was one of the earliest types of light source. Modulated sources, such as mechanically chopped tungsten light bulbs and electronically modulated gas arc lamps, have succeeded the railroad flares.
In deliberate attempts to jam missile trackers, the tracking area is saturated with suspected beacon frequencies, attempting to cover the normal span of optical beacon frequencies that may be utilized. Jamming sources for optical beacons include tungsten flare and xenon arc lamps. These jammers are high average intensity devices operated at relatively low frequencies (less than 100 KH.sub.z).